<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<style type="text/css"></style>
		<script  type="text/javascript">
			//变量   弱类型
			
			var st1Age1 = 10;
			var st1Age2 = 10;
			
			var st1Age3 ;
			st1Age3 = 50;
			
			
			var st1Name1 = 'zhangfei'
			var st1Name2 = '刘备';
			var st1Name3 = "我的偶像是： '刘备' ";
			
			{
				//注册在全局 windows 
				// let myVar1 = 3.1415;
				var myVar1 = 3.1415;
				
			}
			
			console.log(myVar1);
			
			//定义常量  不允许 修改 定义常量的时候 需要赋初始值
			const  pi = 3.1415;
			//pi = 5;
			let area = 2*pi*5;
			console.log(area)
			
			
			
			//流程控制语句
			
			//数据类型
			
			
			//API
			
			
			
			
		</script>
	</head>
	<body>
		121112121221
		
	</body>
</html>